KILIS, Turkey — The bloody conflict in Syria spilled across two borders Monday, killing a cameraman in Lebanon and wounding at least five people in a refugee camp in Turkey as gunfire flew across the tense frontiers, authorities said.

The violence came as a U.N.-brokered peace plan all but collapsed and bolstered fears that the uprising could spark a broader conflagration by sucking in neighboring countries.

Ali Shaaban, a cameraman for the Al Jadeed television station, was filming in Lebanon’s northern Wadi Khaled area when a bullet pierced his chest, Lebanese security officials said. The gunfire came from the nearby Syrian village of Armouta, the officials said.

Mr. Shaaban, who was born in 1980, died on the way to the hospital, the officials said on condition of anonymity in line with regulations.

His colleague, reporter Hussein Khreis, said the team heard heavy gunfire around them from all sides, “falling like rain.” Mr. Shaaban was inside a car when he was struck, Mr. Khreis said.

“If you see the car, you would think it was in a war zone,” Mr. Khreis said on Al Jadeed TV. “It is completely destroyed from the bullets.”

He said they waited for more than two hours for the army and some residents to come and pull them out to safety.

“I ask forgiveness from Ali’s family because I couldn’t do anything for him,” he said, breaking into tears.

Earlier Monday, Syrian forces fired across the border into a refugee camp in Turkey, wounding at least five people, authorities said.

The Syrian soldiers were believed to be firing at rebels who tried to escape to the refugee camp after ambushing a military checkpoint, according to the Britain-based Syrian Observatory for Human Rights, citing a network of sources on the ground.

Turkey shelters thousands of refugees who have fled Syria as President Bashar Assad tries to crush a revolt against his regime. The United Nations estimates that some 9,000 people have been killed in Syria since March 2011, when the uprising began.

The Syrian revolt began with mostly peaceful protests against Mr. Assad’s regime, a family dynasty that has ruled the country for four decades. But in the face of a relentless military assault on protests, the opposition has become increasingly militarized.

Now, the uprising resembles an armed insurgency, and there are fears the country is spiraling toward civil war. Former U.N. Secretary-General Kofi Annan, the U.N.-Arab League envoy to Syria, brokered a cease-fire that was supposed to begin Tuesday, but the plan is in tatters.

Syrian troops were meant to pull out of population centers by Tuesday morning, but the government on Sunday introduced a new demand — saying it cannot withdraw without written guarantees from opposition fighters that they will lay down their arms. Syria‘s main rebel group rejected the government’s demands.

The Syrian opposition and Western leaders have been skeptical all along that Mr. Assad would live up to his commitment to a truce because he has broken similar promises in the past and escalated attacks on opposition strongholds in the days leading up to the cease-fire deadline.

Turkey hosts some 24,000 Syrian refugees, including hundreds of army defectors, and has floated the idea of setting up a buffer zone inside Syria if the flow of displaced people across its border becomes overwhelming.

The two countries share a 566-mile border, and parts of southern Turkey near Syria are informal logistics bases for rebels, who collect food and other supplies in Turkey and smuggle them to comrades across the border.

According to the Syrian Observatory for Human Rights, the fighting along the Turkish border began before dawn Monday when rebel fighters attacked Syrian soldiers manning a checkpoint near the Turkish border, killing six soldiers.

Rami Abdul-Rahman, a spokesman for the Observatory, said the troops then kept firing as they pursued eight wounded rebels who escaped to the camp just across the border in Turkey, sending bullets whizzing across the frontier.

According to the Observatory, the shooting wounded five people in the camp, which is next to the Oncupinar border post near the town of Kilis in Gaziantep province.

The Observatory reported that two people later died of their injuries, but that report could not be immediately confirmed.

The provincial governor, Yusuf Odabas, said five people were wounded: three Syrians, one Turkish translator and one Turkish policeman. The translator was in the camp to try to help calm an anti-Assad protest, he said. The governor said Turkish military forces did not return fire.

Ankara, which has been among Mr. Assad’s harshest critics, summoned the Syrian charge d’affaires in response to the shooting and called for an immediate halt to the gunfire.

Mr. Annan is scheduled to visit to one of the refugee camps in Hatay province, bordering Syria, on Tuesday afternoon, Turkey’s Foreign Ministry said.

“Annan’s one-hour visit to Hatay tomorrow is critical; he will see the situation himself,” Naci Koru, Turkey’s deputy foreign minister, said, according to state-run TRT television.

Mr. Koru also said the deadline for the troop withdrawal has become “void at this stage.”

Mr. Annan has been on a diplomatic push to rally support for his cease-fire deal. The international community, which so far is unwilling to contemplate military intervention, has had little leverage over Syria.

But Iran, Russia and China have been Mr. Assad’s strongest supporters. Mr. Annan already has traveled to Moscow and Beijing, and he was expected in Tehran on Tuesday.

On Monday, Russia was hosting Syrian Foreign Minister Walid Moallem.

It is not clear whether Moscow will try to pressure Syria to comply with the cease-fire plan, though Russia said Monday it may send its observers to Syria as part of a potential U.N. monitoring mission.

Also Monday, Human Rights Watch said it has documented the killings by Syrian forces of 85 civilians, including women and children, and the summary executions of at least 16 wounded or captured opposition fighters.

“In a desperate attempt to crush the uprising, Syrian forces have executed people in cold blood, civilians and opposition fighters alike,” said Ole Solvang, a researcher for the group. “They are doing it in broad daylight and in front of witnesses, evidently not concerned about any accountability for their crimes.”

The New York-based group said it only included cases corroborated by witnesses but has received many more reports of similar incidents.